Browsing by Author "Retief, Francois"

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    Bronchoscopy in children with COVID‐19 : a case series
    (John Wiley & Sons, 2020) Goussard, Pierre; Van Wyk, Lizelle; Burke, Jonathan; Malherbe, Annemie; Retief, Francois; Andronikou, Savvas; Mfingwana, Lunga; Ruttens, Dries; Van der Zalm, Marieke; Dramowski, Angela; Da Costa, Aishah; Rabie, Helena
    Introduction: The coronavirus disease‐2019 (COVID‐19) era is a challenging time for respiratory teams to protect their patients and staff. COVID‐19 is predominantly transmitted by respiratory droplets; in the clinical setting, aerosol generating procedures pose the greatest risk for COVID‐19 transmission. Bronchoscopy is associated with increased risk of patient‐to‐health care worker transmission, owing to aerosolized viral particles which may be inhaled and also result in environmental contamination of surfaces. Methods: We describe our experience with the use of modified full‐face snorkeling masks for pediatric bronchoscopy procedures in four COVID‐19 infected children when filtering facepieces/respirators were in limited supply. Results: Bronchoscopy was urgently required in four children, and could not be delayed until COVID‐19 test results were available. During the pandemic peak, when respirators were in short supply, modified full‐face snorkel masks (SEAC Libera, SEAC, Italy) were worn by the bronchoscopy team. Each mask was fitted with an O‐ring, adapter, and heat and moisture exchanger filter. To date, there have been no COVID‐19 infections among the bronchoscopy team staff, whereas the overall Hospital staff COVID‐19 prevalence rate has exceeded 13.5% (667/4949). Conclusion: Emergency bronchoscopy procedures on COVID‐19 infected patients or patients with unknown infection status can be safely performed using modified full‐ face snorkel masks.
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    The ecology of spotted hyena,Crocuta crocuta, in Majete Wildlife Reserve, Malawi
    (Stellenbosch : Stellenbosch University, 2016-03) Retief, Francois; Leslie, Alison J.; Martins, Quinton; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: The management of predators plays an important role in conservation management today because of the intensive management requirement of small fenced off protected areas. Apex predators such as spotted hyena, Crocuta crocuta, are situated at the top of food chains and have the ability to influence the composition and density of meso-predators and herbivores. Knowledge of apex predators through research can assist in effective management decisions which will ensure ecosystem functioning. Majete Wildlife Reserve (MWR) in the south of Malawi, is a 700km2 reserve, which had noinformation on the resident spotted hyena population until this study. The aims of this study were to gather and make available as much information as possible on the ecology of this apex predator in the reserve for management purposes. A total of 47 camera traps were stationed throughout the reserve for 22 months from 2013 - 2015 and from these data population size, the number of clans (groups), home range size and activity patterns were determined. Faecal analysis was performed to identify the preferred species preyed upon. The reserve has two small, low density resident spotted hyena populations, each with a large home range. These are distinct traits of hyenas residing in arid regions with a clumped resource distribution. The activity patterns of MWR hyenas were similar to East African hyenas in some aspects but peaks in activity differed between the two populations. A total of 17 prey species were identified, with some obvious preferred species. Based on the results from this study, is it recommended that management should make decisions which would favour an increase in the hyena population. At this stage, further lion, Panthera leo, reintroductions should be avoided, as they are the number one competitor of spotted hyena. Both prey and hyena numbers should be monitored in the future to determine whether the hyena population might be in an Allee effect, in which case hyena reintroduction may be considered to restore the balance. It is also suggested that local communities should be educated about hyenas and their role in the environment. This would increase the protection of hyena clans outside the reserve boundaries. These populations are needed for genetic diversity in the MWR hyena population since contact between the populations has been found. Genetic diversity is important for the long term conservation of small populations such as the spotted hyena population in MWR.
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    The effect of a plyometric training programme on selected physical capacities of rugby players
    (Stellenbosch : University of Stellenbosch, 2004-12) Retief, Francois; Venter, R.; University of Stellenbosch. Faculty of Education. Dept. of Sport Science.
    ENGLISH ABSTRACT: The purpose of this study was to investigate the influence of a six-week plyometric training programme on the explosive power, speed and agility as well as certain physiological characteristics and the physical fitness of rugby players. Thirty subjects, that include the first and second rugby teams of the Paul Roos Gymnasium participated in the study. After a thorough evaluation of their medical history, their health status was confirmed as being “apparently healthy” and fit for participation in the project. The subjects were divided into two groups. The experimental group followed a specially designed plyometric training programme in addition to their conventional rugby training, while the control group persisted with the conventional rugby training for the season. Body fat percentage was measured and specific girth measurements were taken to assess physiological changes. Cardiovascular fitness was evaluated by means of the threeminute step test and muscle endurance by means of the push-up and sit-up tests in order to assess the physical fitness of the subjects. The explosive power, speed and agility of the subjects were assessed by means of the agility test [T-drill], ten-meter speed test, Sargent vertical jump test, depth jump test, standing triple jump and the medicine ball chest pass. All measurements and tests were taken before and after the six-week intervention programme of plyometric training. With regards to physiological changes the results showed that the plyometric training programme had a positive effect on the experimental group. The body fat percentage of the experimental group showed a significant decrease and the circumference of their thighs, calves, arms and waist increased. Their chest circumferences did, however, not increase, which might be due to the fact that the plyometric exercises were more specifically aimed at the lower body muscle groups. The results pertaining to physical fitness were mixed. There was a significant improvement (p<0,01) in the cardiovascular fitness of the experimental group while that of the control group stayed relatively constant (p=1,0). With regards to muscle endurance, the control group fared significantly better in the push-up test than the experimental group, while the experimental group fared significantly better in the sit-up test than the control group. The six-week plyometric intervention programme had a statistically significant effect on the performance of the experimental group as compared to the control group, when biomotor skills were assessed. It was concluded that the addition of the specific plyometric exercises to a conventional rugby-training programme would improve the speed, explosive power and agility of rugby players significantly. Beneficial anthropometric changes as well as improved cardiovascular fitness would be additional benefits of a plyometric training programme. The findings of this research suggest that the value of plyometric exercises to motor skills, specific physiological characteristics and physical fitness should not be underestimated and that the trainers and coaches should be informed in this regard. To establish the positive effects of plyometrics as a functional cross training regime for rugby players, more comprehensive research is, however, recommended.
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    Investigation of a high-speed serial bus between satellite subsystems
    (Stellenbosch : Stellenbosch University, 2003-04) Retief, Francois; Treurnicht, J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The aim of this thesis is to investigate the implementation of a high-speed serial bus based on the IEEE Std 1394-1995 specification for use in a microsatellite. Earth observation microsatellites carry imagers (or cameras) that take photographs of the earth. Each photograph generates a large volume of digital data that has to be transferred to either a storage device, a RF transmission unit or a video processing device. Traditionally, the connection between such systems were dedicated serial bus systems that were custom designed for just that purpose. This thesis will investigate the the implementation of a generic alternative to such a custom serial bus. The IEEE 1394 serial bus will allow many devices and subsystems to be connected to the serial bus and will allow these different subsystems to exchange data between each other. As an example implementation, a real-time video link between two points using the IEEE 1394 serial bus will be developed.